How Can I Dynamically Select Columns in LINQ Queries?

Dynamic columns in linq selection

When the list is unknown, the specific column in the LINQ query may be challenging. However, there is a solution involving the Lambda expression passed to Select.

Consider the following data class:

In order to dynamically select a specific column, you can use the Createnewstatement method to dynamically create lambda expressions:

<code class="language-csharp">public class Data
{
    public string Field1 { get; set; }
    public string Field2 { get; set; }
    public string Field3 { get; set; }
    public string Field4 { get; set; }
    public string Field5 { get; set; }
}</code>

This method uses the list of the comma to separate the list as a string, and dynamically generates a lambda expression. This expression initializes a new data object using a specified field.

<code class="language-csharp">private Func<Data, Data> CreateNewStatement(string fields)
{
    var xParameter = Expression.Parameter(typeof(Data), "o");
    var xNew = Expression.New(typeof(Data));

    var bindings = fields.Split(',')
        .Select(o => o.Trim())
        .Select(o =>
        {
            var mi = typeof(Data).GetProperty(o);
            var xOriginal = Expression.Property(xParameter, mi);
            return Expression.Bind(mi, xOriginal);
        });

    var xInit = Expression.MemberInit(xNew, bindings);
    var lambda = Expression.Lambda<Func<Data, Data>>(xInit, xParameter);
    return lambda.Compile();
}</code>

Then you can use the Createnewstatement method to create lambda expressions and pass it to select:

This will return a sequence with a Data object filled in a specified field. Please note that this technology is suitable for the unknown field when compiling. If the selected field is static, the conventional LAMBDA expression or reflex -based method is more efficient.

<code class="language-csharp">var result = list.Select(CreateNewStatement("Field1, Field2"));</code>

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